A variety of spacers have been proposed and utilized for IGUs including metal spacers as well as spacers fabricated from plastic or other insulative material. The present invention relates to metallic spacers.
By way of a brief review of spacer development, early spacers were assembled from four individual linear spacer members. These members were connected at their ends to define right-angle corners thereby forming a complete rectangular spacer. More specifically, molded plastic or fabricated metal corner segments, generally referred to as "corner keys", were employed to join the individual spacer members and to retain the requisite rectangular shape. Illustrative of this spacer technology are U.S. Pat. Nos. 2,173,664; 3,105,274; 3,280,523; 3,380,145; and 4,080,482.
Pre-formed corner keys, however, require that the spacer be fully assembled in its finished rectangular form prior to application of the sealant to each of the spacer's four segments. Sealant applicators or extruders must therefore apply the sealant one segment at a time as the spacer is rotated or "cartwheeled" to orient successive segments in position adjacent the sealant applicator.
To avoid the complexities of cartwheel sealant application, a "folding" variation of the corner key was developed. Folding keys are inserted into the respective spacer segment ends in a "linear" configuration, thereafter, the several corners may be deformed or folded to complete each right-angle corner. One advantage of this approach is the retention of a linear geometry, i.e., the four interconnected segments are laid-out and retained in an elongate, linear configuration and may therefore be fed to a "linear extruder" for the application of sealant in this linear form. Linear sealant extruders are less complex and expensive than their cartwheel counterparts. The spacer, following sealant application, is thereafter folded to its finished rectangular form. Examples of folding corner keys may be seen in U.S. Pat. Nos. 4,357,744; 4,513,546; 4,530,195 and 4,546,723.
The field of "integral" or "continuous" spacers represents the next and logical extension of spacer technology. The present invention pertains to integral spacers. Integral spacers are characterized by a single, generally metallic, member of length equal to the perimeter of the associated IGU and having "corner structures" integrally formed along the length thereof whereby the single spacer structure will be bent and formed, at appropriate time, into its finished rectangular form.
It will be appreciated that integral spacers offer several advantages over their multi-member ancestors including their inherent suitability for linear extrusion (of sealant); the ease of handling a single member structure; and the concomitant savings in both assembly time and material cost (as separate corner keys are not required).
Not surprisingly a myriad of integral spacer topologies have been proposed. U.S. Pat. Nos. 4,431,691 and 4,597,232 suggest radiussed corners, apparently in lieu of so-called "corner structures" found in the remaining integral spacers considered hereinafter. The uncontrolled bending of material to form a corner, however, invariably causes deformation or buckling of the spacer sidewalls in the corner region which, in turn, renders it difficult to seal the spacer to the planar glass surface.
For this reason, virtually all known integral spacers have incorporated appropriate "corner structures" to eliminate or minimize this material deformation in the corner regions. One well-known approach has been the use of fully mitered corners in which all sidewall material that would otherwise "interfere" or "deform" upon spacer folding is physically removed prior to folding. The opposed end surfaces of the adjacent spacer sidewalls abut in a "picture-frame" like manner without actual, forceful engagement there between.
Some of the earliest uses of the fully mitered corner may be found in the present applicants' own "filter frame" products in which plural "miter-defining" notches were stamped at appropriate spaced locations along a single elongate member which member was thereafter roll-formed into a U-shaped channel and folded into a finished rectangular filter-element retaining frame member. See U.S. Pat. Nos. 2,869,694; 3,478,483; and 4,084,720. Examples of fully mitered corners found in window spacers can be found in the "Super Spacer" (a product and trademark of Edgetech I.G. Ltd. of Ottawa, Canada); United Kingdom Patent Application No. 2 104 139 A; United Kingdom Patent No. 349,875; and French Patent Specification No. 2,449,222.
Most recent vintage integral spacers have departed from the fully mitered corner and have, instead, adopted various "corner structures" in which some portion or all of the sidewall material associated with the corner region is retained. As noted, to assure a proper gas-tight seal to the window panes, the outside surfaces of the sidewalls must remain substantially planar through the corner regions and consequently the excess sidewall corner material must be made to buckle inwardly to form interior "pleats".
To this end, "weak zones" have been described, for example, by stamping a plurality of radial "score lines" into the sidewalls--at the corner regions thereof--preferably while the spacer stock remains flat, i.e., prior to the roll-formation of its U-shaped cross-section. To assure that these weak zones buckle correctly (i.e., inwardly), the weak zones are "deformed, or dished, inwardly" prior to spacer folding (corner formation).
Applicants refer to these integral spacers--in which the integrity of the sidewall is maintained throughout the corner--as continuous sidewall spacers. Examples include U.S. Pat. Nos. 5,255,481; 5,295,292; 5,313,761, and 5,351,451.
It will be observed that each of the above-listed continuous sidewall spacers share a common structural feature, namely, an open-interior U-shaped cross-section. Originally spacers were of a closed-form design in order to retain the desiccant pellets therein. With the subsequent development of pumpable desiccant matrices that contain adhesive, or to which adhesive may be applied, it is no longer necessary to close the inwardly facing surface of the spacer--the desiccant matrix is literally glued within the spacer channel--whether of a closed or an open, U-shaped form.
The U-shaped spacer topology offers several fabrication-related advantages including the previously noted ease and flexibility of desiccant application, i.e., the ability to apply the desiccant before, during, or after formation of the channel itself. But of potentially greater significance is the "absence" of the fourth side, i.e., the inner surface, which surface would "bunch-up" thereby interfering with the folding formation of the corner. Clearly, urging further pleats into the corner interior--as would be required of a fully enclosed, four-sided spacer--would result in pleat interference and the unpredictable and uncontrolled deformation of the corner sidewalls.
Notwithstanding these limitations, a few fully enclosed, integral spacers have been developed. Such spacers generally include a "block" or "plug" positioned within the spacer channel at, or adjacent to, the corner regions to retain the desiccant, thereafter, a fully mitered notch is made through both sidewalls and the fourth or inner surface. In this manner, the corners of the fully enclosed integral spacer may be formed by the conventional folding thereof without the destructive interference caused by the buckling of the sidewalls or inner wall. Exemplary of this spacer is the spacer manufactured on the model RDF-1 system, itself manufactured by Besten, Inc. of Chagrin Falls, Ohio. Besten also manufactured a model RDF-2 system that produced a similar fully enclosed spacer, but where the spacer's "corner structure" notches were punched prior to spacer roll-forming.